14-3-3: Detection of elevated levels of the 14-3-3 protein in the cerebrospinal fluid (CSF) may support a CJD diagnosis in appropriate context.

Akinetic mutism: A state where a person can no longer move or talk due to damage to the brain, but the person is awake (not comatose) and their eyes are open and can follow what is going on around them.

Aphasia: A loss of the ability to produce and/or understand language due to injury to the brain.

Apraxia: The loss of the ability to perform tasks that require remembering patterns or sequences of movements (like waving goodbye).

Ataxia: Wobbliness, unsteady walk and clumsiness usually caused by damage to the cerebellum, a part of the brain which controls balance and coordination.

Autosomal dominant: Individuals with autosomal dominant diseases have a 50-50 chance of passing the mutated gene on to each of their children.

Bovine Spongiform Encephalopathy (BSE): A prion disease found in cows, also known as "mad cow disease."

Brain biopsy: A brain biopsy is a surgical procedure on a live patient to remove a small specimen of tissue from the brain. Because the specimen may be taken from a non-affected part of the brain and result in a false negative, a brain biopsy should only be performed if other conditions besides CJD are suspected.

Creutzfeldt-Jakob disease (CJD): Creutzfeldt-Jakob disease is a rare, degenerative, invariably fatal brain disorder. Typically, onset of symptoms occurs at about age 60. There are three major categories of CJD: sporadic CJD, genetic CJD and acquired CJD. The first concern is to rule out treatable forms of dementia, such as encephalitis or chronic meningitis. Other tests may support the diagnosis (14-3-3/Tau/RT-QuIC; CSF, EEG and brain MRI.) The only way to confirm a diagnosis of CJD is by neuropathologic examination.

Dementia: A deterioration of intellectual faculties, such as memory, concentration and judgment, that affects daily functioning. It is sometimes accompanied by emotional disturbance and personality changes.

Diffusion Weighted MRI: An MRI imaging technique that can be used to help diagnose CJD.

Dysphagia: Difficulty in swallowing due to problems in nerve or muscle control.

Gerstmann-Sträussler-Scheinker Syndrome (GSS): Gerstmann-Sträussler-Scheinker disease (GSS) is a very rare, neurodegenerative brain disease. Onset of the disease usually occurs between the ages of 35 and 55. In the early stages, patients may experience varying levels of ataxia (lack of muscle coordination), including clumsiness, unsteadiness, and difficulty walking. As the disease progresses, the ataxia becomes more pronounced and most patients develop dementia.

Human prion disease: Prion diseases or transmissible spongiform encephalopathies (TSEs) are a family of rare progressive neurodegenerative disorders that affect both humans and animals. They are characterized by a spongy appearance of the brain and accumulation of abnormal prion proteins.

Iatrogenic(iCJD) is due to transmission of prion disease through specific medical procedures like human growth hormone and corneal and dura mater transplants obtained from cadavers affected by prion disease.

MRI (magnetic resonance imaging): A radiology technique that uses magnetism, radio waves and a computer to produce non-invasive, high quality images of internal structures of the body. An MRI is painless, does not use x-ray radiation and is a powerful tool for delineating brain structure.

Mutation: A permanent change in the DNA or RNA - the molecular "blueprints" that direct the building of proteins. Mutations can be helpful, neutral or harmful and can be caused randomly or by environmental factors.

Myoclonus: Sudden, involuntary jerking or twitching of a muscle or group of muscles.

Prions: Transmissible proteins that cause prion diseases.

Pulvinar sign: Symmetrically increased signal intensity in the pulvinar region (posterior part of the thalamus) relative to the signal intensity in other deep and cortical gray matter areas on an MRI; the presence of this MRI feature may suggest a vCJD diagnosis in the appropriate clinical context.

Real-Time Quaking Induced Conversion: (RT-QuIC): RT-QuIC can detect the actual abnormal prion protein and is 98.5% diagnostic of prion disease should it be detected in the spinal fluid.

Scrapie: A prion disease in sheep and goats.

Spinal Tap: A doctor collects the cerebrospinal fluid (CSF) by doing a lumbar puncture (spinal tap) in which a very thin needle is gently inserted in your lower back between two vertebrae, the bony structures that make up your spine. It is used to look for infections, inflammation, and markers that may suggest prion disease (14-3-3/Tau/RT-QuIC.)

Sporadic CJD: The cause of "classic" or "sporadic" CJD is unknown, which means it occurs in people without any known risk factors or gene mutations. Typical symptoms include imbalance and incoordination, memory loss and impaired thinking, and psychiatric symptoms such as anxiety or depression. Once the symptoms do appear, CJD typically progresses very quickly and is usually fatal within a few months of symptom onset. sCJD typically affects people in their 60s and is rarely seen in people younger than 40 years old. Sporadic CJD is the most common form of prion disease (85 percent.)

Tau: A protein in the body that aids in the cellular structure (cytoskeleton) and cellular transportation. Elevated levels in CSF may be suggestive of prion disease.

Transmissible Spongiform Encephalopathy (TSE): A family of rare progressive neurodegenerative disorders that affect both humans and animals and are caused by prions (e.g., prion diseases.)

Variant CJD (vCJD) is a very rare form of prion disease caused by the ingestion of food contaminated with bovine spongiform encephalopathy (BSE). The vast majority of these cases have occurred in European countries, where the BSE epidemic occurred. There have been no documented cases of vCJD associated directly with beef consumption in the United States.